The present invention relates to a planetary-gear automatic transmission and, in particular, to a planetary-gear automatic transmission having at least eight forward gear positions, wherein for shifting the individual gear positions, shifting devices formed by clutches and/or brakes are provided, and for actuating the shifting devices, shift actuators are provided which generate assigned actuating forces.
The state of the art consists of an automatic transmission having eight forward gears. For increasing the possibility of lowering fuel consumption, automatic-transmission concepts having nine or more gears are being explored. As the number of gears increases, however, the installation space available in the vehicle for the transmission is increasingly becoming a bottleneck.
Planetary-gear automatic transmissions are shifted by the closing or opening of clutches and/or brakes. In the case of diverse transmission concepts, which have a plurality of forward gears, up to now at least some of the clutches of the transmission had to be placed such that they are accessible only by constructively very high-expenditure rotary transmission leadthroughs or, in the case of an electric operation, by way of slip ring actuators.
FIG. 1 is a schematic illustration of an example of a planetary-gear automatic transmission 1, where the two clutches 2 can be operated only by way of very high technical expenditures. At least, it is not possible to arrange a shift actuator in the area of the two clutches because an element that rotates during the operation is situated radially outside the two clutches 2.
The arrangement of shift actuators in the case of the clutches 2 of the transmission illustrated in FIG. 2 has similar difficulties.
It is an object of the invention to provide a planetary-gear automatic transmission, particularly a planetary-gear automatic transmission having at least eight forward gear positions, which has an advantageous construction with respect to the arrangement of the shift actuators.
This and other objects are achieved by a planetary-gear automatic transmission, particularly, a planetary-gear automatic transmission having at least eight forward gear positions, wherein for shifting the individual gear positions, shifting devices formed by clutches and/or brakes are provided, and for actuating the shifting devices, shift actuators are provided which generate assigned actuating forces. The planetary-gear automatic transmission is constructed such that all shift actuators are arrangeable directly on or directly in the area of the assigned shifting devices.
The starting point of the invention is a planetary-gear automatic transmission, particularly a planetary-gear automatic transmission having at least eight forward gear positions. For shifting the individual (forward) gear positions, shifting devices are provided. The shifting devices can be formed by clutches or brakes. For the actuation of the shifting devices, clutches or brakes, shift actuators are provided. The term “shift actuator” should be interpreted extremely broadly. In principle, it includes all devices suitable for generating actuating forces for actuating the shifting devices. Particularly hydraulic or electric shift actuators are relevant to planetary-gear automatic transmissions.
In accordance with the invention, the planetary-gear automatic transmission is constructed such that all shift actuators of the transmission can be arranged or are arranged directly on or directly in the area of the assigned shifting devices.
The invention is therefore clearly distinguished from “interlocked transmission concepts”, as illustrated, for example, in FIGS. 1 and 2. The individual shifting devices have “force introduction points”. Force introduction points are “points” at which actuating forces are introduced into the concerned shifting device by the assigned shift actuator. According to a further aspect of the invention, the force introduction points of all shift actuators are accessible from a case of the planetary-gear automatic transmission. This is specifically not so in the case of the clutches 2 illustrated in FIGS. 1 and 2.
Preferably, all shift actuators are fastened directly to the case of the transmission or to a supporting device assigned to the corresponding shift actuator. The supporting device or the supporting devices is connected with the transmission case.
According to a further aspect of the invention, the planetary-gear automatic transmission has at least one “multiple shift actuator”. A “multiple shift actuator” is a shift actuator to which at least two shifting devices are functionally assigned. Three or more shifting devices may also be assigned to a shift actuator. The higher the “rank” of such multiple shift actuators, the more compact the construction of the transmission tends to be.
It may be provided that a shift actuator, to which two or more shifting devices are functionally assigned, is provided for optionally actuating: (a) one shifting device assigned to it, (b) simultaneously several of the shifting devices assigned to it, or (c) simultaneously all of the shifting devices assigned to it.
With respect to the construction, it is advantageous for a multiple shift actuator for the shifting devices functionally assigned to it to not have to be actuated simultaneously. It may correspondingly be provided that, of the shifting devices functionally assigned to a shift actuator, always only one can be actuated or is actuated.
The invention is suitable particularly for planetary-gear automatic transmissions which have four or more planetary gear sets and six or more shifting devices.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.